Tropical Grasslands (1992) Volume 26, 7–11

Correlations among potential selection criteria for improving the feeding value of forage sorghums

C. MULCAHY, D.A. HEDGES, G.G. RAPP and J.L. WHEELER

CSIRO Division of Animal Production, Armidale, New South Wales, Australia

Abstract

To facilitate the breeding and selection of forage sorghums of improved feeding value a study was made of correlations among important indicators of feeding value. Eleven commercial and developmental lines of sorghum comprising 7 interspecific hybrids of Sorghum bicolor × S. sudanense, 1 hybrid of S. sudanense, 1 cultivar derived from S. halepense × S. roxburghii × S. arundinaceum and 2 grain sorghum types (S. bicolor) were field grown in rows in 1988 and 1989. Their relative preferences to sheep and cattle were determined by estimating standing dry matter before and after grazing and 12 physical and chemical attributes of the forage were measured. In both years hydrogen cyanide potential was positively and significantly correlated with leaf/stem ratio (P < 0.001) and with leaf width (P < 0.001). Leaf width and hydrogen cyanide potential were consistently related to percentage eaten by grazing stock. The 2 grain sorghum types ranked the highest in these 2 attributes and were the least preferred. Both sheep and cattle showed a preference for forages with narrower leaves and lower hydrogen cyanide potentials. Consideration of such correlations could enhance selection and breeding programs.

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